Safety device for installation in a gas-supply system, in particular, an acetylene-supply system

ABSTRACT

Relevant specifications in the field of gas supply provide for different safety devices for installation in a gas-supply system, in particular, an acetylene-supply system. To provide such a safety device, which is characterized by a compact structure and a high level of operational reliability, this invention proposes that a valve body ( 1 ) incorporates an over-pressure valve ( 4; 104 ) of a quick-action shut-off device, a control valve ( 3; 103 ) of a pressure-limiting device, and a safety valve ( 2; 102 ), whereby the safety valve ( 2; 102 ) can be fluidically connected to the over-pressure valve ( 4; 104 ) and the control valve ( 3; 103 ), and closes either when the over-pressure valve ( 4; 104 ) opens due to an inlet pressure that is above the inlet-pressure limit value or when the control valve ( 3; 103 ) opens due to an outlet pressure that is above an outlet-pressure limit value.

RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.14/260,691 filed Apr. 24, 2014, published as U.S. published applicationNo. 2014-0318642 A1, which is herein incorporated by reference in itsentirety.

TECHNICAL BACKGROUND

The invention refers to a safety device for installation in a gas-supplysystem, in particular, an acetylene-supply system, where a main pressureregulator relieves gas fed in at inlet pressure to outlet pressure.

In its simplest form, the gas-supply system can be a gas cylinder, atank or another type of container. Several containers can also beconnected to one another, so when one container becomes empty, thesystem is able to switch to a different container which is still full.

The gas-supply system feeds the gas to a tapping point. The gas to betapped is pressurized and in this respect already represents a certainhazard potential for users and the environment. In principle, the safetydevice is suitable for installation in all gas-supply systems of thistype. However, it has a particularly beneficial effect when used withcombustible or toxic gases, such as methane, propane, natural gas,hydrogen, liquid gas, carbon monoxide, halogens and suchlike, andespecially with acetylene-gas-supply systems.

Acetylene (C₂H₂) is known for being highly flammable and, at hightemperature or pressure, decomposes into its elements suddenly ifheated. Depending on the circumstances, this decomposition may have adetonating effect, thus endangering people, the surroundings, and thesystem. Therefore, the maximum operating pressure (outlet pressure) inacetylene extraction lines is usually limited to 1.5 bar ofover-pressure. In addition, various safety devices are provided infittings or piping. These devices are defined, for example, foracetylene systems in general in TRAC 207 (Technische Regeln fürAcetylenanlagen und Calciumcarbidlager, “technical rules for acetylenesystems and calcium-carbide stores”) and for acetylene manifold systemsspecifically in standard EN ISO 14114:1999 (Acetylene manifold systemsfor welding, cutting and allied processes—General requirements).

Safety devices on the inlet-pressure side feature manual or automaticquick-action shut-off devices as per EN ISO 14114:1999, Section 3.6, gasnon-return valves, and flashback arrestors. Gas non-return valvesprevent the acetylene from flowing back, while flashback arrestors cooldown and hold back hot decomposition fumes.

Quick-action shut-off devices are installed in particular in piping orfittings on the inlet-pressure side of the manifold system and shut thisoff manually or automatically in the event of acetylene decomposition inorder to stop the spread of said decomposition even before the mainpressure regulator is reached, preventing it from getting through to theoutlet-pressure side of the pressure regulator. In line systems whereexplosions may be expected to start from two sides, such quick-actionshut-off devices must be designed in duplicate for both sidesaccordingly. They are also known as decomposition arrestors and musteven be capable of withstanding potential acetylene decomposition whenthere is a detonative effect, where pressures of over 100 MPa (1000 bar)can occur.

PRIOR ART

The safety devices are installed at a suitable position in supply linesor fittings. DE 43 08 801 C2, for example, describes an acetylene-supplysystem composed of cylinder bundles, which are connected to one anotherby means of a computer-controlled pneumatic switchover system. Aquick-action valve and a purge valve are fitted on the inlet-pressureside of the line system, that is, upstream of the main pressureregulator, along with a decomposition arrestor directly upstream of thetapping point.

There are no construction details provided for these safety devices. Ifthe pressure rises above a predefined level, acetylene gas can bedischarged into the open through the purge valve. However, the dischargeof acetylene to a secure location is still associated with danger andenvironmental pollution; therefore, it is fundamentally undesirable (ENISO 14114:1999, Section 4.1.1.f).

A quick-action valve for installation in the high-pressure line of anacetylene bundle system is already familiar from DE-AS 20 01 954; in theevent of an explosion, this valve works as a gas seal and a flashbackarrestor simultaneously. It consists of a housing with an internal hole,in which there is a cylinder that permits movement in the axialdirection and is fixed on a steel wire; if the valve is open, theacetylene gas flows around this cylinder. The pressure wave of anexplosion causes the cylinder, due to the deformation of the supportwire, to press against a sealing point of the internal hole, forexample, against a conical wall made of lead, thus closing the internalhole. The flashback arrestor, which is located after the seal in thedirection of flow, consists of a steel-wool plug fixed in the housing'sinternal hole.

The quick-action valve does have a simple construction, but it alsocomes with disadvantages, one being that the closing behavior cannot bereliably reproduced and another that the valve is destroyed when usedand has to be removed and replaced before the gas-supply equipment canbe operated again.

Another basic problem associated with reliably supplying acetylene gasis that the pressure regulator's outlet pressure is subject to a certaindegree of uncertainty too. This uncertainty is based, for example, onthe possibility of a gradual increase in pressure due to a deviation ora sudden pressure increase caused by a controller defect. In order toprevent this, EN ISO 14114:1999, Section 3.7, recommends that a“pressure-limiting device” be used.

A pressure regulator taking the form of a gas-cylinder valve cap, whichfulfills this function, is already familiar from GB 2 342 416 B. To thisend a housing is provided, in which a valve piston is positioned onbearings between a front and rear seal that permit movement in the axialdirection. The valve piston has a front end facing the gas cylinder witha small cross-sectional area and an opposite end with a largercross-sectional area, which a spiral spring rests against and whichprotrudes into a pressure chamber sealed off by the rear seal, which agas inlet opens into.

The inlet pressure applied at the gas-cylinder outlet against thesmaller effective cross-section is sufficient to lift the piston valveoff the front seal against the pressure of the spiral spring in order toenable gas to be tapped from the gas cylinder. Some of the tapped gas isfed back via a bypass to the pressure chamber through its gas inlet atan outlet pressure set on the pressure regulator. The rear end of thevalve piston protrudes into this chamber. As the outlet pressure rises,the pressure on the rear, larger cross-sectional area of the valvepiston increases until this pressure, combined with the spring force ofthe spiral spring, is sufficient to press the valve piston against thefront seal, thus stopping gas being tapped any further.

In this way the actual outlet pressure applied is regulated and limitedin relation to the inlet pressure. However, the valve is only held inits closed position by means of the, although increased, outletpressure. If the inlet pressure rises, for example, due to an acetylenedecomposition reaction, there is a risk of the valve opening anddestroying the pressure-limiting device as a result.

OBJECT TO BE SOLVED

The object which this invention aims to solve is to provide a safetydevice for a gas-supply system, in particular, an acetylene-supplysystem, which is characterized by a compact structure and a high levelof operational reliability, and which avoids the disadvantages explainedabove that are associated with known equipment.

SUMMARY

The invention solves this task by providing a safety device whichcomprises a valve body incorporating an over-pressure valve of aquick-action shut-off device, a control valve of a pressure-limitingdevice, and a safety valve, whereby the safety valve can be fluidicallyconnected to the over-pressure valve and the control valve, and closeseither when the over-pressure valve opens due to an inlet pressure thatis above an inlet-pressure limit value or when the control valve opensdue to an outlet pressure that is above an outlet-pressure limit value.

The safety device represented by this invention comprises an automaticquick-action shut-off device and an automatic pressure-limiting device.In contrast to the state of the art, however, these functions are notprovided in different places within the gas-supply system's line system;rather, they are realized in a single fitting, which is designed forinstallation in the high-pressure area.

In order to combine the quick-action shut-off device and thepressure-limiting device, both functions have been developed inside asingle shared valve housing, which is essentially manufactured as amonolithic, multiple-part block, for example. On the other hand, thefunctions themselves have been designed as valves, namely, as anover-pressure valve and a control valve, with these valves in turn beingconnected to a safety valve, which serves as a joint shut-off valve forboth functions. The safety valve shuts off the supply line and,consequently, any further gas supply as soon as either the over-pressurevalve or the control valve opens. Therefore, it ideally fulfills thespecifications for a pressure-controlled shut-off valve as per EN ISO14114:1999, Annex B.

The over-pressure valve opens if the inlet pressure (operating pressure)exceeds a predefined limit value. The limit value can be adjusted or ispreset at the factory. It may be, for example, 1.2 times the standardmaximum cylinder or line pressure, for instance, 30 bar. If this valueis exceeded, a major defect must be expected, involving acetylenedecomposition, for example, and the gas-supply line is closedautomatically. As such, this function fulfills the standardspecifications for an automatic quick-action shut-off device (EN ISO1411:1999, Section 3.6.2).

The control valve opens if the outlet pressure exceeds a predefinedlimit value. The outlet pressure is the operating pressure for gastapping, which is set by the main gas-flow-rate controller. To this end,the control valve features a gas inlet at which the outlet pressure isapplied. This limit value too can be adjusted or is preset at thefactory. It may be, for example, 1.2 times the standard target value forthe operating pressure, for instance, 1.8 bar at a target operatingpressure of 1.5 bar. As such, this function fulfills the standardspecifications for a pressure-limiting device as per EN ISO 14114:1999,Section 3.7.

In normal operation the over-pressure valve and control valve areclosed; the safety valve is open and allows gas to flow unimpeded. Theover-pressure valve and control valve are both fluidically connected tothe safety valve. In this context a “fluidic connection” is understoodto mean that, if a connection is open, there will be full or extensivepressure compensation between the pressurized areas which arefluidically connected, irrespective of whether these pressurized areasare connected to one another directly—via a single shared connectionline—or indirectly—via several connected lines, cavities or pressurizedareas.

The interaction between the different valves and functions inside asingle fitting enables the valve housing to benefit from a compactdesign. If this safety device is installed, there is no need for arelief valve or overflow valve either.

A preferred embodiment of the safety device invention is for the safetyvalve to feature an inlet-pressure gas inlet, an inlet-pressure gasoutlet, and, between the gas inlet and gas outlet, a safety-valvechamber. This chamber can be closed via a safety-valve closing element,ideally a safety-valve piston that permits movement inside the chamberin an axial direction and opens with the inlet pressure. The chamber canbe divided into a front pressure chamber and a rear pressure chamber,whereby the safety-valve closing element, ideally the safety-valvepiston, protrudes into the front pressure chamber facing theinlet-pressure gas inlet with a first, smaller effective cross-section,and whereby the safety-valve closing element, ideally the safety-valvepiston, protrudes into the rear pressure chamber facing theinlet-pressure gas outlet with a second, larger effective cross-section,and whereby the rear pressure chamber and the front pressure chamber canboth be fluidically connected to the over-pressure valve and the controlvalve via pressure-compensation lines.

The gas is transferred via the safety valve, which to this end featuresa gas inlet and a gas outlet, whereby the gas at each is at inletpressure. The closing element that permits movement in the axialdirection inside the safety-valve chamber—for example, the safety-valvepiston—opens with the inlet pressure applied at the gas inlet and, innormal operation, allows gas to flow from the gas inlet to the gasoutlet unimpeded.

The safety-valve chamber is divided into a front pressure chamber and arear pressure chamber by the closing element (referred to hereafter asthe “piston”). It is important that the effective cross-section for thegas pressure acting on the piston is smaller in the front pressurechamber than in the rear pressure chamber. This difference in theeffective cross-section means that the safety-valve piston is broughtinto its closed position at the latest when the pressure in the rearpressure chamber is at the same level as the pressure in the frontpressure chamber. This interrupts any further gas supply. Ideally, thesafety valve is designed as a piston valve. However, it can also featurea different closing element that is equivalent to the piston, forexample, a diaphragm.

The safety-valve piston ideally features a cavity and a piston wallsealed off from the safety-valve chamber area by area, whereby thecavity has at least one cross hole that extends through the piston walland into an area which is connected to the front pressure chamber whenthe safety valve is open and is sealed off from the front pressurechamber when the safety valve is closed.

The safety-valve piston which is able to move against the spring forcein the axial direction inside the safety-valve chamber features a cavityat its rear end. This cavity has one or more cross holes, which openinto the front pressure chamber if the safety valve is open. If thesafety valve is closed, these through holes are sealed off from thefront pressure chamber.

Both the front and the rear pressure chamber can be fluidically—i.e.,directly or indirectly—connected to the over-pressure valve and thecontrol valve via pressure-compensation lines. The pressure-compensationlines are pressurized if the respective valve (over-pressurevalve/control valve) is open. Ideally, if the valve is open, therespective pressure-compensation lines are pressurized with the inletpressure prevailing at the inlet-pressure gas inlet, so the rearpressure chamber of the safety-valve chamber is then pressurized withthis inlet pressure too and the safety valve closes accordingly.

To this end, the control valve is connected to the safety valve via apressure-compensation line, through which gas flows into the controlvalve at inlet pressure when the control valve is open and the opensafety valve closes.

If the control valve is open, gas flows into the control valve at inletpressure through this pressure-compensation line and from therecontinues through the other pressure-compensation line into the rearpressure chamber of the safety valve, which then closes. This happens asexplained above in the description of the safety valve, that is, becausethe effective cross-section for the gas pressure acting on thesafety-valve piston is larger in the rear pressure chamber than in thefront pressure chamber. This difference in the effective cross-sectioncauses the safety-valve piston to always be brought into and held in theclosed position when the pressures in the two pressure chambers are atthe same level. The inlet pressure always acts as the holding forcehere, never the outlet pressure.

Since the control valve of the pressure-limiting device is to open ifthere is an excessively high outlet pressure, it must be connected to agas source in which the outlet pressure is applied. A tried-and-testedconfiguration in this context is for the control valve to feature anoutlet-pressure gas inlet for the gas, which is connected to acontrol-valve chamber closed against the outlet-pressure gas inlet up tothe predefined outlet-pressure limit value by means of a control-valveclosing element, ideally a control-valve piston, which permits movementinside the chamber in an axial direction, whereby when the control valveis open, the pressure-compensation lines are open and fluidicallyconnect the control-valve chamber to the front pressure chamber and therear pressure chamber.

This connection ensures, for example, a preferred embodiment of thesafety device invention, in which the control-valve piston features acavity and a piston wall sealed off from the control-valve chamber areaby area, whereby the cavity is fluidically connected to the rearpressure chamber and has at least one cross hole that extends throughthe piston wall and into an area which is sealed off when the controlvalve is closed and is fluidically connected to the front pressurechamber when the control valve is open.

The control-valve piston which is able to move against the spring forcein the axial direction inside the control-valve chamber features acavity at its rear end, which is in turn connected to the rearsafety-valve pressure chamber via a pressure-compensation line. Inaddition, one or more cross holes through the piston wall are providedin the cavity. If the control valve is closed, the cross hole designedas a through hole opens into an area of the piston outer wall which issealed to the outside, for example, between sealing rings fitted aboveand below the through hole. However, if the control valve is open—thatis, if the outlet pressure is above the limit value—this through holeopens into an area of the piston outer wall which is connected to thefront pressure chamber of the safety-valve chamber via thepressure-compensation line.

If the control valve is open, gas flows into the cavity of thecontrol-valve piston at inlet pressure via this fluidic connection andfrom there continues through the other pressure-compensation line intothe rear pressure chamber of the safety-valve chamber, which causes thesafety valve to close immediately.

The control-valve chamber and the control-valve piston are designedadvantageously such that when the control valve is in the open position,a pressure acting in the closing direction has a larger effectivecross-section than the pressure acting in the opening direction.

The fact that the total forces acting on the control-valve piston in theclosing direction are greater than the forces acting in the openingdirection ensures that the control valve is closed again immediately assoon as the open position is reached. The gas which is at inlet pressureand applied at the through hole of the piston may have to be enclosed tothis end, which can also be achieved by means of seals above and belowthe through hole once it has occupied its valve open position. One ofthe forces acting on the control-valve piston in the closing directionis the restoring force of a spring and the back pressure from the rearpressure chamber, which also corresponds to the inlet pressure, whoseeffect on the control-valve piston can however be increased by acomparatively larger effective cross-section.

The control valve is also preferably designed as a piston valve.However, it can also feature a different closing element that isequivalent to the piston, for example, a diaphragm.

In terms of the over-pressure valve of the quick-action shut-off device,a tried-and-tested configuration is for it to feature an over-pressurechamber connected to the inlet-pressure gas inlet. This chamber has anover-pressure-chamber opening, which is closed by means of a closingelement that is able to move in the axial direction and is fluidicallyconnected to the rear pressure chamber via a pressure-compensation line.

At the over-pressure valve—unlike the control valve—the supply pressurecorresponds to the inlet pressure actually prevailing at theinlet-pressure gas inlet and in the front pressure chamber. This is alsoapplied at the valve opening of the over-pressure chamber, for example,via a pressure-compensation line fluidically connected to the frontpressure chamber. A spring provided in the over-pressure chamber definesthe minimum pressure force above which the closing element is moved inthe axial direction and releases the valve opening. At a target inletpressure of up to 25 bar, such as is standard for acetylene containers,for example, the minimum pressure is around 30 bar, for instance.

If the over-pressure valve is open, gas flows at the current inletpressure to the rear pressure chamber through the pressure-compensationline provided for this purpose. This moves the safety-valve piston, asdescribed above based on the control valve, into the closed position andany further gas supply is stopped immediately. No discharge of the gasfrom the over-pressure valve into the open is provided for; theover-pressure chamber is closed—with the exception of thepressure-compensation line mentioned and any gas discharge lines to adisplay instrument or similar.

Ideally, the closing element is pressed against theover-pressure-chamber opening by means of a spring located in theover-pressure chamber; this element has a larger effective pressurecross-section on its side facing the over-pressure chamber than on itsopposite side.

The spring force and the difference in the effective cross-sectionresults in a force which acts explicitly on the closing element in theclosing direction. This ensures that the over-pressure valve is onlyopen temporarily, for around as long as it takes to perform pressurecompensation with the rear pressure chamber. The safety valve thencloses so a pressure at approximately the same level as theinlet-pressure limit value or higher remains in the over-pressurechamber.

The pressure thus remaining in the over-pressure chamber acts togetherwith the spring on the closing element in the closing direction andprevents the over-pressure valve from opening again, or makes thisprocess difficult.

In the event that a safety valve which has already been activated, i.e.,closed causes a further pressure rise in the inlet-pressure line,however, the over-pressure valve must be opened again in the interestsof ensuring a reliably closed safety valve.

To this end a tried-and-tested configuration is for the over-pressurevalve and the safety valve to be coordinated with one another such that,if the safety valve is closed, the forces acting on the safety-valvepiston in the closing direction are greater than the forces acting onthe closing element in the closing direction.

If the over-pressure valve opens again, the pressure applied in the rearpressure chamber and acting on the safety-valve piston in the closingdirection also increases, thus guaranteeing that the safety valve cannotopen.

If the safety valve has been activated, i.e., the gas supply has beenunavoidably interrupted due to the limit value for the outlet pressurebeing exceeded or the limit value for the inlet pressure being exceeded,the rear pressure chamber is subject to over-pressure. It contains gasand, if acetylene is used, may contain a proportion of gaseous acetylenedecomposition products. It is not possible to continue using the safetydevice in this condition; it must be removed or—ideally—vented.

A particularly advantageous embodiment of the safety device invention isprovided for this purpose, where the valve body incorporates a ventvalve. This valve in turn features a vent-valve chamber, which is closedvia a closing element that can be mechanically actuated and, thus, movedin the axial direction, and is fluidically connected to the rearpressure chamber via a pressure-compensation line.

The fault which caused the safety valve to be activated must berectified. Irrespective of whether the fault came from an increasedoutlet pressure or an increased inlet pressure, the valve opened as aresult (control valve/over-pressure valve) automatically returns to itsinitial position—that is, the closed position. Therefore, the vent-valvechamber can be opened safely by moving the closing element, so gassubject to over-pressure is able to discharge from the vent-valvechamber, as well as from all lines and cavities fluidically connected toit, and from the rear pressure chamber in particular. The gas flow beingdischarged depends on the over-pressure of the gas and the volume filledwith gas and can be very low.

Thanks to the pressure reduction in the rear pressure chamber, thesafety-valve piston moves back to its initial position due to the gaspressure applied in the front pressure chamber—ideally assisted by aspring located in the safety-valve chamber. The safety valve is thusopen again and ready for operation. Provided that maintenance has beenperformed and indicates that the safety device is undamaged, it does notneed to be removed.

The pressure in the vent-valve chamber can reach up to 1000 bar. A highpressure makes it difficult to actuate the closing element. Atried-and-tested configuration in this context is for the closingelement to be moved by means of a threaded bolt, which can be screwed inor out easily even at a high pressure force. However, it may benecessary to ensure that the vent valve is closed again prior torecommissioning by loosening the threaded bolt.

To enable a user to identify that a fault is present straightaway, apreferred embodiment of the safety device features a valve bodyincorporating a display instrument, which has a hole containing aninspection element positioned on bearings that permit movement in theaxial direction. This element seals the hole and allows for a displaypressure chamber at the base of the hole; this chamber is fluidicallyconnected to the rear pressure chamber via a pressure line.

When the safety valve is activated—due to whatever cause—the rearpressure chamber is subjected to over-pressure, which is propagated viathe pressure line into the display pressure chamber at the base of thedisplay element's hole. This causes the display element—ideally workingagainst the force of a return spring—to be partially pushed out of thehole, making it easily identifiable (due to its signal color too, forexample). Once the fault has been rectified and any ventilation carriedout, the display element can be sunk into the hole again or moved thereautomatically by means of the return spring.

As regards a particularly high level of operational reliability andreliability of the safety device, it has proved beneficial for thecontrol valve and/or the over-pressure valve to be designed as apreassembled and encapsulated module.

The preassembly of the module (also referred to hereafter as the“cartridge”) enables the respective function to be preset accurately atthe factory, resulting in a high level of operational reliabilityalongside reproducible functionality. The encapsulation preventsunauthorized access to the cartridge and the predefined settings beingchanged, or makes these actions difficult. Sealing can be provided forinspection purposes.

In addition, it is easier, more reproducible, and more reliable toreplace the preassembled module than to replace the module's individualcomponents.

It has proved particularly beneficial for the preassembled module tofeature a sealing cap, which provides visual information on themaintenance status.

When the module is maintained/inspected, the sealing cap must be removedin order to check the module is functioning correctly and to carry outany readjustment or resetting work, if necessary. The entire module canalso be replaced as part of this procedure. Afterwards, the checked orreplaced module is fitted with a sealing cover, for example, a blindcap, which shows the most recent maintenance/inspection status, similarto a decal from a technical inspectorate. The visual information cantake the form of a colored year-specific ID or show the date, forexample.

PREFERRED EMBODIMENTS

The invention is explained in more detail below by illustrativeembodiments and a drawing. The drawing shows a schematically in:

FIG. 1 a first embodiment of the safety device invention in alongitudinal section,

FIG. 2 a detail from FIG. 1 showing a larger depiction of the safetyvalve,

FIG. 3 a detail from FIG. 1 showing a larger depiction of the controlvalve,

FIG. 4 a detail from FIG. 1 showing a larger depiction of theover-pressure valve,

FIG. 5 another embodiment of the safety device invention in alongitudinal section,

FIG. 6 a detail from FIG. 5 showing a larger depiction of the safetyvalve,

FIG. 7 a detail from FIG. 5 showing a larger depiction of the controlvalve,

FIG. 8 a detail from FIG. 5 showing a larger depiction of theover-pressure valve,

FIG. 9 the embodiment of the safety device invention from FIG. 5 with aview of the longitudinal side,

FIG. 10 the embodiment of the safety device invention from FIG. 5 with aview of the front face, partially truncated, and

FIG. 11 the embodiment of the safety device invention from FIG. 5 in athree-dimensional depiction.

EXAMPLE 1

The embodiment of the safety device depicted in FIG. 1 is designed forinstallation in the supply line of an acetylene system in whichacetylene is drawn from cylinders or cylinder bundles. The safety deviceis designed as a multiple unit valve and is installed in the system'shigh-pressure area—upstream of the main pressure regulator.

The valve body 1 consists of a two-part, essentially monolithic brassblock. Both block parts (housing 1A and housing cover 1B) are screwedtogether and sealed. Sealing elements are basically depicted in FIGS. 1to 4 as black surface entities. The valve body 1 features a number ofholes, which accommodate the following components: a safety valve 2(stop valve), a control valve 3, an over-pressure valve 4, a displayinstrument 5, and a vent valve 6.

Safety Valve 2

The valve body 1 has a central through hole, into which the gasconnections 7; 8, which serve to connect the safety device to theacetylene supply line, are screwed on both sides.

Between a gas inlet 15 and a gas outlet 16, the safety valve 2 isdesigned as a piston valve that opens with the inlet pressure. Thisvalve is depicted in FIG. 1 and in larger form in FIG. 2. Thesafety-valve piston 10 is able to move in the axial direction within thesafety-valve chamber between a valve-closed position and a valve-openposition. FIG. 1 depicts the open position; the piston movement in theclosing direction is indicated by block arrow A. In the closed position,the safety-valve piston 10 divides the safety-valve chamber into a frontpressure chamber 11 and a rear pressure chamber 12.

The safety-valve piston 10 features a cavity 14, which is designed as ablind hole, opens into the gas outlet 16 on the side opposite to theflow, and is connected to the front pressure chamber 11 via four throughcross holes 17. It is designed as a double piston, whose cylinder jacketfeatures areas with two different external diameters. The area 19 withthe maximum external diameter protrudes into a spring chamber, which isencapsulated by means of sealing rings against the ingress of acetyleneor decomposition gases. A sinuous spring 13 rests against the top sideof the surrounding area 19; this spring keeps the piston 10 in the openposition during normal operation. The bottom side of this area 19protrudes into the rear pressure chamber 12, where it has acomparatively large piston area. As a result, the safety-valve piston 10has a larger effective cross-section to act against the gas pressure inthe rear pressure chamber 12 than against the gas pressure in the frontpressure chamber 11.

FIGS. 1 and 2 depict the safety valve 2 in the open position. Asindicated by the two direction arrows, the acetylene gas coming from theinlet-pressure gas inlet 15 flows into the front pressure chamber 11,through the cross holes 17 into the cavity 14, and from there to theinlet-pressure gas outlet 16 unimpeded.

If the safety valve 2 is closed, a sealing ring 18 fitted to the frontpiston end of the safety-valve piston 10 rests against the inner wall ofthe safety-valve chamber, thus sealing the cross holes 17 off from thefront pressure chamber 11. The different effective cross-sections in thefront and rear pressure chambers 11; 12 ensure that the safety-valvepiston 10 is always brought into and held in the closed position whenthe pressures in the respective pressure chambers 11; 12 are at the samelevel. The pressure prevailing in the rear pressure chamber 12 alwaysacts as the holding force here. This pressure is always the inletpressure, as explained in more detail below.

If the safety valve 2 is closed, the supply of further acetylene gas isinterrupted. The safety valve 2 closes if either the control valve 3 orthe over-pressure valve 4 is open. The safety valve 2 also closes ifthere is a pressure rise originating on the side of the gas outlet 8, ascan occur if acetylene decomposes in the relevant gas line between thesafety device and the main pressure regulator, for example. In thisrespect the safety valve 2 also acts as a non-return valve.

Control Valve 3

The control valve 3 is inserted in another hole in the valve body 1.This hole runs parallel to the middle hole for the safety valve 2.

The control valve 3 is depicted in FIG. 1 and in larger form in FIG. 3.It is part of a limiting device for the outlet pressure, which is set to1.5 bar by default. The control valve 3 serves to interrupt the supplyof acetylene if the main pressure regulator indicates a significantdeviation or a defect, which manifests itself as a gradual or suddenincrease in the outlet pressure. The limit value is defined as 20% abovethe target value, i.e., 1.8 bar. The control valve 3 opens above thispressure.

To this end, acetylene gas at outlet pressure is fed to the controlvalve 3 from the outlet-pressure area of the main pressure regulatorthrough a bypass line symbolized by the direction arrow, which ends atthe elbow fitting 31. In its normal condition, the control valve 3 isclosed. In this state the gas pressure applied at the outlet-pressuregas inlet 32 for the acetylene gas is not sufficient to move thecontrol-valve piston 33 in the opening direction against the pressure ofa sinuous spring 34 resting against the opposite end. The pistonmovement in the opening direction is indicated by block arrow B.

Similar to the safety-valve piston 10, the control-valve piston 33 alsofeatures a cavity 35, which is designed as a blind hole and leads to thepiston outer wall through the cross holes 36. The cavity 35 isfluidically connected to the rear pressure chamber 12 of the safetyvalve 2 via a pressure-compensation line 37. The cross holes 36 reachthe piston outer wall at a longitudinal section, which is closed offfrom the outside if the control valve 3 is closed, thanks to sealingrings fitted on both sides. When the control-valve piston 33 moves inthe opening direction, the longitudinal section concerned finally alignswith the sealed cross holes 39 of the valve sleeve 38. This opens thecontrol valve 3. Inlet pressure is constantly applied at the cross hole39, since it is fluidically connected to the front pressure chamber 11via the other pressure-compensation line 30 and the gas inlet 15.

If the outlet pressure exceeds the preset limit value of 1.8 bar, thecontrol valve 3 opens the fluidic connection to the front pressurechamber 11 of the safety-valve chamber, so acetylene gas at inletpressure flows into the cavity 35 of the control-valve piston 33 andfrom there through the pressure-compensation line 37 to the rearpressure chamber 12 of the safety-valve chamber, which causes the safetyvalve 2 to close straightaway, as explained above.

If the control valve 3 is open, so too are the pressure-compensationlines 30; 37, which are connected to one another via the control-valvepiston 33. This ensures that the front pressure chamber 11 and the rearpressure chamber 12 are at the same pressure, i.e., the inlet pressure,so the safety valve 2 closes.

Over-pressure Valve 4

The over-pressure valve 4 is also inserted in a hole in the valve body,which runs perpendicular to the middle hole. The over-pressure valve 4is depicted in FIG. 1 and in larger form in FIG. 4. It is part of theautomatic quick-action shut-off device. The operating pressure (inletpressure) in the acetylene supply line is between 4 and 25 bar,depending on the fill level of the acetylene container. Theover-pressure valve 4 serves to interrupt the acetylene gas flow as soonas the inlet pressure exceeds the maximum operating pressure by 20%,i.e., 30 bar.

To this end, the over-pressure valve 4 features an over-pressure chamber46, inside which a sinuous spring 42 presses a slide valve 43, which isable to move in the axial direction, with a sealing lip 44 against anopening, thus closing it. The current prevailing inlet pressure of theacetylene gas is constantly applied at this opening through apressure-compensation line 45 that is connected to the inlet-pressuregas inlet 15.

FIGS. 1 and 4 depict the closed position; the piston movement in theopening direction is indicated by block arrow C. If the over-pressurevalve 4 is open, acetylene gas at the current inlet pressure flowsthrough a pressure-compensation line 41 to the rear pressure chamber 12,thus closing the safety valve 2.

The slide valve 43 has a larger effective pressure cross-section on itsside facing the over-pressure chamber than on its other side, socombined with the spring force of the sinuous spring 42, this results ina force acting in the closing direction. This ensures that theover-pressure valve 4 is only open temporarily.

Even if the inlet pressure rises still further, the safety valve 2should always remain closed; the over-pressure valve 4, on the otherhand, can open. The design achieves this through the spring forces ofthe respective sinuous springs 13; 42 and the difference between theeffective pressure faces of the respective closing pistons 10; 19; 43acting in the closing direction. Overall the over-pressure valve 4 andthe safety valve 2 are coordinated with one another such that, if thesafety valve 2 is closed, the forces acting on the safety-valve piston10 (or, more precisely, on the larger diameter area 19) in the closingdirection are greater than the forces acting on the slide valve 43 inthe closing direction.

In normal operation, therefore, the over-pressure valve 4 and thecontrol valve 3 are closed; the safety valve 2 is open and allows gas toflow unimpeded. However, the safety valve 2 shuts off the acetylenesupply line as soon as either the over-pressure valve 4 or the controlvalve 3 opens. Therefore, it fulfills the specifications for apressure-controlled shut-off valve as per EN ISO 14114:1999, Annex B,the standard specifications for an automatic quick-action shut-offdevice as per EN ISO 1411:1999, Section 3.6.2, and for apressure-limiting device as per EN ISO 14114:1999, Section 3.7.

Vent Valve 6

If the safety valve 2 is closed due to the limit value for the outletpressure or the limit value for the inlet pressure being exceeded, it isnot possible to continue using the safety device without taking furthersteps.

In this condition, the rear pressure chamber 12 is pressurized. A ventvalve 6 is provided in the valve body 1 for ventilation purposes. Thevent valve 6 is inserted in another hole in the valve body 1, which runsparallel to the middle hole. It features a vent-valve chamber 61, whichis connected to the rear pressure chamber 12 via a pressure-compensationline 62. The vent-valve chamber 61 is closed by means of a cap 63 with asealing lip 64. This cap can be pushed in the direction of thevent-valve chamber 61 using a set screw 66 (to the left as depicted inFIG. 1). This causes the vent-valve chamber 61 to open, so thepressurized acetylene gas is able to discharge from the vent-valvechamber 61, as well as from all lines and cavities fluidically connectedto it, and from the rear pressure chamber 12 in particular. Once the setscrew 66 has been loosened, the restoring force of a spring 65 bringsthe cap 63 back to its initial position, so the vent valve 6 is closedagain.

This ventilation causes the safety-valve piston 10 to move back into itsinitial position due to the gas pressure applied in the front pressurechamber 11 and assisted by the compression spring 13, so the safetyvalve 2 is once again open and ready for operation.

Activation Indicator 5

The valve body 1 also contains a hole to accommodate the activationindicator 5. This hole runs parallel to the middle hole. The activationindicator 5 shows that a fault is present. To this end, a coloredindicator pin 51 with a foot 52, which is sealed off from the inner walland rests against the base of the hole, is incorporated in the hole. Thebase of the hole is connected to the rear pressure chamber 12 via apressure-compensation line 54.

If the safety valve 2 is closed, the rear pressure chamber 12 ispressurized. This pressure is propagated via the pressure-compensationline 54 to the base of the hole of the display element 5, which causesthe indicator pin 51 to be pushed out of the hole against the force of areturn spring 53 resting against the foot 52 (to the right as depictedin FIG. 1). Once the fault has been rectified and ventilation carriedout via the vent valve 6, the indicator pin 51 sinks back into the holeautomatically thanks to the return spring 53.

EXAMPLE 2

An embodiment of the safety device invention modified from that depictedin FIG. 1 is explained below based on FIGS. 5 to 11. As can be seen fromthe figures, this embodiment features a number of sealing rings arrangedin pairs, whereby one of the two sealing rings in each case serves asthe “sacrificial ring”. If this ring is destroyed through acetylenedecomposition, the other sealing ring continues to guarantee the sealingfunction. Furthermore, some of the single valve units integrated in thevalve body 1 have been designed as preassembled, self-contained units,or “cartridges”, which can be fitted and set at the factory.

These and other differences will be explained in more detail below.Inasmuch as the same reference numbers are used as in FIGS. 1 to 4, theyrefer to the same or equivalent components or parts of the safety deviceas have already been explained for the embodiment described inIllustration 1.

The safety device is designed for installation in the supply line of anacetylene system in which acetylene is drawn from cylinders or cylinderbundles. The safety device is designed as a multiple unit valve and isinstalled in the system's high-pressure area—upstream of the mainpressure regulator.

Here too, the valve body 1 consists of a two-part, essentiallymonolithic and cylinder-shaped brass block with two block parts (housing1A and housing cover 1B) that are screwed together and sealed. Sealingelements are depicted as black surface entities in this instance too.Both the housing 1A and the housing cover 1B feature holes, whichaccommodate the following components: a safety valve 102 (stop valve), acontrol valve 103, and an over-pressure valve 104 in the housing 1A, anda display instrument 105 and a vent valve 106 in the housing cover 1B.

Safety Valve 102

The valve body 1 has a central through hole, into which the gasconnections 7; 8, which serve to connect the safety device to theacetylene supply line, are screwed on both sides. On the embodimentdepicted in FIG. 5, the gas connections 7; 8 are arranged in a straightconfiguration. The valve body 1 contains a connection hole 107, closedby a dummy plug 108, for an alternative, angled arrangement. Therefore,the safety device can either be installed in the straight-line or angledconnection variant, depending on the on-site conditions.

Between a gas inlet 15 and a gas outlet 16, the safety valve 102 isdesigned as a piston valve that opens with the inlet pressure. Thisvalve is depicted in FIG. 5 and in larger form in FIG. 6. Thesafety-valve piston 110 is able to move in the axial direction withinthe safety-valve chamber between a valve-closed position and avalve-open position. FIG. 5 depicts the open position; the pistonmovement in the closing direction is indicated in FIG. 6 by block arrowA. In the closed position, the safety-valve piston 110 divides thesafety-valve chamber into a front pressure chamber 11 and a rearpressure chamber 12.

The safety-valve piston 110 features a cavity 14, which is designed as ablind hole, opens into the gas outlet 16 on the side opposite to theflow, and is connected to the front pressure chamber 11 via a number ofthrough cross holes 117. It is designed as a double piston, whosecylinder jacket features areas with two different external diameters.The area 19 with the maximum external diameter protrudes into a springchamber, which is encapsulated by means of sealing rings against theingress of acetylene or decomposition gases. A sinuous spring 13 restsagainst the top side of the surrounding area 19; this spring keeps thepiston 110 in the open position during normal operation. The bottom sideof this area 19 protrudes into the rear pressure chamber 12, where ithas a comparatively large piston area. As a result, the safety-valvepiston 110 has a larger effective cross-section to act against the gaspressure in the rear pressure chamber 12 than against the gas pressurein the front pressure chamber 11.

The outer jacket of the piston 110 is sealed off from the hole of thevalve body 1 by means of O-rings on both sides of the larger diameterarea 19. These O-rings are integrated in grooves on the piston 110 andarranged in pairs, whereby one of the O-rings in each case serves as the“sacrificial O-ring”. The sacrificial O-ring is the one exposed to thedecomposition conditions first in the event of acetylene decomposition,where pressures can reach over 1000 bar and high temperatures can occur.In the case of the O-ring pair on the side opposite to the flow, forexample, this is the O-ring identified by reference number 113; ifacetylene decomposes in the gas line between the safety device and themain pressure controller, this O-ring will be the first to be subjectedto the flow-back of decomposition products.

FIGS. 5 and 6 depict the safety valve 102 in the open position. Asindicated by the two direction arrows 111 and 112, the acetylene gascoming from the inlet-pressure gas inlet 15 flows into the frontpressure chamber 11, through the cross holes 117 into the cavity 14, andfrom there to the inlet-pressure gas outlet 16 unimpeded.

If the safety valve 102 is closed, the front piston end of thesafety-valve piston 110 rests against a sealing ring 118, which isembedded in a groove running all around the inner wall of the gas inlet15. The sealing ring 118 which is integrated in the valve body 1 in thisway remains fixed in the groove even under high mechanical stress.

As an additional protective measure the safety-valve piston 110 featuresa metallic sealing band 114 (FIG. 6) running all the way around, whichis located in a piston face recess and points in the closing directionA. If acetylene decomposition occurs, the end of the piston 110 strikesthe sealing ring 118 and the sealing band 114 strikes the sealing face115 of the valve housing 1 simultaneously to create a tight metalliccontact surface, which continues to function as a seal even if thesealing ring 118 fails and interrupts or at least significantly reducesthe supply of further acetylene gas.

In the closed state, the cross holes 117 are sealed off from the frontpressure chamber 11. The different effective cross-sections in the frontand rear pressure chambers 11; 12 ensure that the safety-valve piston110 is brought into and held in the closed position. The pressureprevailing in the rear pressure chamber 12 acts as the maximum holdingforce here. This pressure is the inlet pressure, as explained in moredetail below.

If the safety valve 102 is closed, the supply of further acetylene gasis interrupted. The safety valve 102 closes if either the control valve103 or the over-pressure valve 104 is open. The safety valve 102 alsocloses if there is a pressure rise originating on the side of the gasoutlet 8, as can occur if acetylene decomposes in the relevant gas sline between the safety device and the main pressure regulator, forexample. In this respect the safety valve 102 also acts as a non-returnvalve.

To make it easier to take a blocked safety valve 102 out of the valvehousing 1, the output-side end of the piston 110 features an internalthread 114. To reduce the risk of solid decomposition products, such aschips, entering the safety valve 102 and, in particular, the sealingarea of the sealing rings, noble-metal filter disks 115 are installedupstream of the gas inlet 15 and the gas outlet 16.

Control Valve 103

The control valve 103 has been designed as a preassembled,self-contained module preset at the factory, which may also be referredto as a “control-valve cartridge”. The control-valve cartridge isinserted in another hole in the valve body 1. This hole runs parallel tothe middle hole for the safety valve 102.

The control valve 103 is depicted in FIG. 5 and in larger form in FIG.7. It is part of a limiting device for the outlet pressure. The controlvalve 103 serves to interrupt the supply of acetylene if the mainpressure regulator indicates a significant deviation from the nominalpressure or a defect, which manifests itself as a gradual or suddenincrease in the outlet pressure.

The level of the outlet pressure corresponds to the nominal pressure atthe consumer. In low-pressure applications this is 0.8 bar, inmedium-pressure applications 1.2 bar, and in high-pressure applications1.5 bar. The activation limit pressure for the control valve 103 isaround 20% above the respective nominal value and is preset at thefactory, for example, to 1.5 bar for the medium-pressure range. However,the activation limit pressure can also be readjusted during operation,as is explained in more detail further below.

Acetylene gas at outlet pressure is fed to the control valve 103 fromthe outlet-pressure area of the main pressure regulator through a bypassline. The bypass line is connected to the control valve 103 via thejacket surface of the valve body 1 and can be seen in FIGS. 9, 10, and11 as the lateral screwed connection 130. This connection opens into anoutlet-pressure gas compartment 132 inside the control-valve cartridge(103), which can be seen in FIG. 7 as a narrow cavity sealed on bothsides and which contains a circlip 131.

In its normal condition, the control valve 103 is closed. In this statethe gas pressure applied at the outlet-pressure gas compartment 132 forthe acetylene gas is not sufficient to move the control-valve piston(133; 134) in the opening direction against the pressure of a sinuousspring 34 resting against it. The piston movement in the openingdirection is indicated by block arrow B.

The control-valve cartridge is sealed to the outside by means of a blindcap 138 and a plug 139, which is installed in a piston head 134 designedwith a hexagon socket. The plug 139 is intended to make unauthorizedaccess to the control-valve cartridge difficult and to preventunintended changes being made to settings. The blind cap 138 is sealedwith a test seal and color-coded, whereby its color indicates thecurrent inspection status (for example, the most recent year ofinspection).

The activation limit pressure of the control valve 103 can be correctedor set to a different value. To this end, the control-valve piston isdivided into two parts: a piston head 134 and a piston rod 133, whichare connected to one another via a thread 136. The overall length of thecontrol-valve piston (133; 134) can be modified using this threadedconnection 136. If the control-valve piston (133; 134) is lengthened,the stroke for activating the valve shortens and, conversely, the strokelengthens if the piston (133; 134) is shortened.

To adjust the activation limit pressure of the control valve 103, theblind cap 138 and the plug 139 are removed and the hexagon socket whichthen becomes accessible is used to turn the thread 136 between thepiston rod 133 and the piston head 134.

This adjustment can also be made during operation, since the accessiblearea of the hexagon socket is sealed off from the rest of the valvechamber by an O-ring. The piston rod 133 features a lateral flat surface137, against which a pin 135 rests. This prevents the piston rod 133from being turned as well when the threaded connection 136 is actuated.

FIGS. 5 and 7 depict the control valve 103 in the closed position. Thevalve sleeve 38 features the cross holes 39, which are sealed on bothsides. One of these seals is realized via an O-ring 140 inserted in agroove on the valve sleeve 38; this O-ring rests against a longitudinalsection of the piston rod 133 adjacent to the flat-surface area. Thecross holes 39 themselves are located in the flat-surface area 137 ofthe piston rod 133 and are connected to a pressure-compensation line 30via a profiled area 142 of the piston rod 133. Inlet pressure isconstantly applied at this line, as it is fluidically connected to thefront pressure chamber 11 via the gas inlet 15.

A rear gas compartment 141 is located at the output-side end of thepiston rod 133; this compartment is connected to the rear pressurechamber 12 of the safety valve 102 via another pressure-compensationline 37.

The outlet-pressure gas compartment 132 is sealed gas-tight from thepressure-compensation line 30 and from the pressure-compensation line 37by means of O-rings. If the control valve 103 is closed, the fluidicconnection between the aforementioned pressure-compensation lines 30 and37 is broken. When the piston rod 133 moves in the opening direction(direction arrow B), however, the chamfer facing the flat surface 137 ofthe piston rod 133 extends into the sealing area of the O-ring 140. TheO-ring 140 is not able to seal the chamfered area and the flat surface137, so the aforementioned pressure-compensation lines 30 and 37 areconnected to one another and, as a result, the control valve 103 isopen.

If the outlet pressure in the outlet-pressure gas compartment 132exceeds the preset limit value, the control valve 103 opens the fluidicconnection to the front pressure chamber 11 of the safety-valve chamber,so acetylene gas at inlet pressure flows into the cavity 141 and fromthere through the pressure-compensation line 37 to the rear pressurechamber 12 of the safety-valve chamber, which causes the safety valve102 to close straightaway, as explained above.

If the control valve 103 is open, so too are the pressure-compensationlines 30; 37, which are connected to one another via the control-valvepiston 133. This ensures that the front pressure chamber 11 and the rearpressure chamber 12 are at the same pressure, i.e., the inlet pressure,so the safety valve 102 closes.

Over-pressure Valve 104

The over-pressure valve 104 has also been designed as a preassembled,self-contained module preset at the factory, which may also be referredto as an “over-pressure-valve cartridge”. The over-pressure-valvecartridge is inserted in a hole in the valve body 1, which runsperpendicular to the middle hole for the safety valve 102. Theover-pressure valve 104 is depicted in FIG. 5 and in larger form in FIG.8. It is part of the automatic quick-action shut-off device.

The operating pressure (inlet pressure) in the acetylene supply line isbetween 4 and 25 bar, depending on the fill level of the acetylenecontainer. The over-pressure valve 104 serves to interrupt the acetylenegas flow as soon as the inlet pressure exceeds the maximum operatingpressure by 20%. The activation limit pressure is preset at the factoryto 30 bar, for example, but it can also be adjusted or readjusted whenpressurized.

To this end, the over-pressure-valve piston is designed as a two-partcomponent consisting of a piston valve 143 and a master piston 144. Asinuous spring 42 is installed between these components (143; 144). Themaster piston 144 is screwed into the over-pressure-valve piston pinbushing 145 by means of a thread 149 and features a hexagon socket onits end face which can be accessed from above. The hexagon socket issealed to the outside by a plug 147, with the over-pressure-valvecartridge (104) being sealed by a blind cap 148 in addition. The colorof the blind cap 148 indicates the current maintenance or inspectionstatus, as has already been explained above in relation to the controlvalve 103. Once the blind cap 148 and the plug 147 have been removed,the hexagon socket of the master piston 144 can be accessed. Turningthis socket enables the spring bias of the sinuous spring 42 to bechanged and, consequently, the activation limit pressure to be correctedor reset.

The over-pressure valve 104 usually features an over-pressure chamber 46sealed by an O-ring 146. The piston valve 143 with sealing lip 44, whichpermits movement in the axial direction, acts against the pressure ofthe sinuous spring 42 to press against and close an opening. The currentprevailing inlet pressure of the acetylene gas is constantly applied atthis opening through a pressure-compensation line 45 that is connectedto the inlet-pressure gas inlet 15.

FIGS. 5 and 8 depict the closed position; the piston movement in theopening direction is indicated by block arrow C. If the over-pressurevalve 104 is open, acetylene gas at the current inlet pressure flowsthrough a pressure-compensation line 41 to the rear pressure chamber 12,thus closing the safety valve 102.

The piston valve 143 has a larger effective pressure cross-section onits side facing the over-pressure chamber 45 than on its other side, socombined with the spring force of the sinuous spring 42, this results ina force acting in the closing direction. This ensures that theover-pressure valve 104 is only open temporarily.

Even if the inlet pressure rises still further, the safety valve 102should always remain closed; the over-pressure valve 104, on the otherhand, can open. The design achieves this through the spring forces ofthe respective sinuous springs 13; 42 and the difference between theeffective pressure faces of the respective closing pistons 10; 19; 43acting in the closing direction.

Overall the over-pressure valve 104 and the safety valve 102 arecoordinated with one another such that, if the safety valve 102 isclosed, the forces acting on the safety-valve piston 110 (or, moreprecisely, on the larger diameter area 19) in the closing direction aregreater than the forces acting on the slide valve 43 in the closingdirection.

In normal operation, therefore, the over-pressure valve 104 and thecontrol valve 103 are closed; the safety valve 102 is open and allowsgas to flow unimpeded. However, the safety valve 102 shuts off theacetylene supply line as soon as either the over-pressure valve 104 orthe control valve 103 opens. Therefore, it fulfills the specificafor apressure-controlled shut-off valve as per EN ISO 14114:1999, Annex B,the standard specifications for an automatic quick-action shut-offdevice as per EN ISO 1411:1999, Section 3.6.2, and for apressure-limiting device as per EN ISO 14114:1999, Section 3.7.

Vent Valve 106

If the safety valve 102 is closed due to the limit value for the outletpressure or the limit value for the inlet pressure being exceeded, it isnot possible to continue using the safety device without taking furthersteps.

In this condition, the rear pressure chamber 12 is pressurized. A ventvalve 106 is provided in the valve body 1 for ventilation purposes. Thevent valve 106 is inserted in another hole in the valve body 1, whichruns parallel to the middle hole of the safety valve 102. It features avent-valve chamber 61, which is connected to the rear pressure chamber12 via a pressure-compensation line 62. A threaded insert 163, whichfeatures a groove in which an O-ring 164 is located, protrudes into thevent-valve chamber 61 and seals it to the outside. The threaded insert163 is screwed into the hole of the valve body 1, where it comes to reston a wall running all the way around the valve body 1 and through thiscontact forms a metallic seal in addition to the seal created by theO-ring 164. The end of the threaded insert 163 which points outwardfeatures a hexagon socket 165 and another external thread onto which athreaded plug 166 with a through hole is screwed. The threaded plug 166also has an external thread, which enables it to be screwed into thehole of the valve body 1.

The threaded insert 163 can be screwed out of the vent-valve chamber 61using the hexagon socket 165 (to the right as depicted in FIG. 5). Ifthe O-ring 164 moves out of its position, this causes the vent-valvechamber 61 to open, so the pressurized acetylene gas is able todischarge from the vent-valve chamber 61, as well as from all lines andcavities fluidically connected to it, and from the rear pressure chamber12 in particular. Screwing the threaded insert 163 into the hole as faras it will go brings the O-ring 164 and the metallic seal back intotheir sealing positions, so the vent valve 106 is closed again.

This ventilation causes the safety-valve piston 110 to move back intoits initial position due to the gas pressure applied in the frontpressure chamber 11 and assisted by the compression spring 13, so thesafety valve 102 is once again open and ready for operation.

Activation Indicator 105

The valve body 1 (or, more precisely, the housing cover 1B) alsocontains a hole to accommodate the activation indicator 105. This holeruns parallel to the middle hole for the safety valve 102. Theactivation indicator 105 shows that a fault is present. To this end, abrass piston 152 is inserted into the hole; this piston works inconjunction with a colored plastic indicator pin 151. On one side theindicator pin 151 is inserted into a blind hole on the brass piston 152,which runs coaxially to the brass piston's longitudinal axis, and on theother side it leads into the through hole of a threaded plug 156. Thethreaded plug 156 has an identical construction to the threaded plug 166of the vent valve 106 and, like this, has an external thread, whichenables it to be screwed into the hole of the valve body 1.

The outer jacket surface of the brass piston 152 is sealed off from theinner wall of the hole in the valve body 1 by means of a pair of O-rings(with a sacrificial O-ring). The base of the hole is connected to therear pressure chamber 12 via a pressure-compensation line 54.

If the safety valve 102 is closed, the rear pressure chamber 12 ispressurized. This pressure is propagated via the pressure-compensationline 54 to the base of the hole of the display element 105, which causesthe brass piston 152 together with the indicator pin 151 to be pushedout of the hole against the force of a return spring 53 (to the right asdepicted in FIG. 5). Once the fault has been rectified and ventilationcarried out via the vent valve 106, the brass piston 152 and theindicator pin 151 sink back into the hole automatically thanks to thereturn spring 53.

FIG. 9 depicts a longitudinal view of the embodiment of the safetydevice invention according to Illustration 2 with the two-part valvebody 1, the gas connections 7 and 8 on both sides for connecting thesafety device to the acetylene supply line, and the gas connection 130for the outlet-pressure bypass line to the control valve 103.

The front view shown in FIG. 10 also depicts a broken-out section withdetails of the gas connection 130 which joins the jacket surface of thevalve body 1 for the outlet-pressure bypass line, as well as the blindcap 138 of the control valve 103.

The three-dimensional depiction of the safety device shown in FIG. 11also shows the blind cap 148 of the over-pressure valve 104, as well asthe dummy plug 108 for an alternative, angled gas connection 7.

The invention claimed is:
 1. A safety device for installation in agas-supply system, where a main pressure regulator regulates an inletpressure of a gas fed thereto to an outlet pressure, said safety devicecomprising: a valve body to which the gas is fed at the inlet pressureand from which the gas is fed at the outlet pressure, an over-pressurevalve of a quick-action shut-off device, said over-pressure valve beingconfigured to open responsive to the inlet pressure being above apredetermined inlet-pressure limit value, a control valve of apressure-limiting device, said control valve being configured to openresponsive to the outlet pressure being above a predeterminedoutlet-pressure limit value, and a safety valve in the valve body andthrough which the gas passes, said safety valve being fluidicallyconnected to the over-pressure valve and the control valve, and whereinthe safety valve closes either when the over-pressure valve opens due tothe inlet pressure being at an inlet pressure level that is above theinlet-pressure limit value, or when the control valve opens due to theoutlet pressure being at an outlet pressure level that is above anoutlet-pressure limit value, wherein the safety valve has aninlet-pressure gas inlet, an inlet-pressure gas outlet, and asafety-valve chamber therebetween, said chamber being configured to beclosed via a safety-valve closing element that is supported so as to bemovable inside the chamber in an axial direction and such that thesafety-valve closing element moves such that the safety valve opens withthe inlet pressure, said chamber being divided into a front pressurechamber and a rear pressure chamber, wherein the safety-valve closingelement protrudes into the front pressure chamber facing theinlet-pressure gas inlet with a first effective cross-section, whereinthe safety-valve closing element protrudes into the rear pressurechamber facing the inlet-pressure gas outlet with a second effectivecross-section that is larger than the first effective cross section, andthe rear pressure chamber and the front pressure chamber are both beingconfigured to be fluidically connected to the over-pressure valve andthe control valve via pressure-compensation lines, wherein thecontrol-valve closing element is a control-valve piston that movesinside the chamber, and wherein the control-valve piston has a pistonwall sealed off from the control-valve chamber, and wherein thecontrol-valve piston has a cavity that is fluidically connected to therear pressure chamber and has at least one cross hole that extendsthrough the piston wall and into an area that is sealed when the controlvalve is closed and fluidically connected to the front pressure chamberwhen the control valve is open.
 2. The safety device as claimed in claim1, wherein the control valve is connected to the safety valve via apressure-compensation line, and wherein gas flows through thepressure-compensation line into the control valve at the inlet pressurewhen the control valve is open, causing the safety valve to close. 3.The safety device as claimed in claim 1, wherein the control valve hasan outlet-pressure gas inlet for the gas, and wherein theoutlet-pressure gas inlet is connected to a control-valve chamber closedagainst the outlet-pressure gas inlet up to the outlet-pressure limitvalue with a control-valve closing element that is supported so at bemovable inside the chamber in an axial direction, and wherein when thecontrol valve is open, the pressure-compensation lines are open andfluidically connect the control-valve chamber to the front pressurechamber and the rear pressure chamber.
 4. The safety device as claimedin claim 1, wherein when the control valve is open, a pressure acting ina closing direction has a larger effective cross-section than a pressureacting in an opening direction.
 5. The safety device as claimed in claim1, wherein the over-pressure valve has an over-pressure chamberconnected to the inlet-pressure gas inlet, and wherein the chamber hasan over-pressure-chamber opening that is closed with a closing elementthat is able to move i an axial direction thereof and is fluidicallyconnected to the rear pressure chamber via a pressure-compensation line.6. The safety device as claimed in claim 5, wherein the closing elementis pressed against the over-pressure-chamber opening by a spring locatedin the over-pressure chamber, and wherein the closing element has alarger effective pressure cross-section on a side thereof facing theover-pressure chamber than on an opposite side thereof.
 7. The safetydevice as claimed in claim 5, wherein the safety-valve closing elementis a piston, and wherein the over-pressure valve and the safety valveare coordinated with one another such that, if the safety valve isclosed, the forces acting on the safety-valve piston in a closingdirection are greater than the forces acting on the closing element inthe closing direction.
 8. The safety device as claimed in claim 1,wherein the valve body incorporates a vent valve, wherein the vent valvehas a vent-valve chamber that is closed via a closing element that canbe mechanically actuated and moved in the axial direction, and thevent-valve chamber is fluidically connected to the rear pressure chambervia a pressure-compensation line.
 9. The safety device as claimed inclaim 8, wherein the closing element can be moved by a threaded bolt.10. The safety device as claimed in claim 1, wherein the valve body hasa display instrument with a hole containing an inspection element thatis positioned on bearings that permit movement in an axial directionthereof, wherein the inspection element seals the hole, and wherein adisplay pressure chamber is located at the base of the hole said displaypressure chamber being fluidically connected to the rear pressurechamber via a pressure line.
 11. The safety device as claimed in claim1, wherein the control valve or the over-pressure valve is apreassembled, encapsulated module.
 12. The safety device as claimed inclaim 11, wherein the preassembled module has a sealing cap thatprovides visual information on the maintenance status.
 13. The safetydevice as claimed in claim 1, wherein the safety-valve closing elementis a safety-valve piston.